Diagnosis and management of interstitial lung diseases (ILDs), caused by lung epithelial injury followed by apoptosis, are often challenging. It has been controversial whether the SIRT1 protein, a principal modulator ...Diagnosis and management of interstitial lung diseases (ILDs), caused by lung epithelial injury followed by apoptosis, are often challenging. It has been controversial whether the SIRT1 protein, a principal modulator of longevity due to caloric restriction, ameliorates or aggravates ILD in animal models. Here we examined the effect of SRT1720, a syn- thetic activator of SIRT1, on bleomycin-induced lung injury in a mouse model and apoptosis in cultured epithelial cells. Oral intubation of SRT1720 over a period of 15 days caused body weight loss and a high mortality rate among bleomy- cin-treated mice. Histological examinations showed that the SRT1720 load increased fibrosis in the bleomycin-treated lung. An analysis of bronchoalveolar lavage fluid revealed remarkably increased numbers of inflammatory cells in the SRT1720-treated group. Moreover, the apoptosis of A549 lung cancer cells, caused by X-ray irradiation and an anti-Fas activating antibody, was promoted by SRT1720. These results indicate that SRT1720 not only aggravates bleomy- cin-induced ILD, but stimulates the apoptosis of physically and biologically stimulated A549 cells. While SIRT1 acti- vators are considered promising for the treatment of conditions such as diabetes mellitus, fatty liver, and chronic ob- structive pulmonary diseases, an excess of food containing SIRT1 activators may be harmful depending on the disease state, especially in the case of acute inflammation.展开更多
The murine peptidylarginine deiminase (PAD) has five isoforms encoded by different genes and participates in a variety of cellular functions through the citrullination of target proteins. The crystal structure of huma...The murine peptidylarginine deiminase (PAD) has five isoforms encoded by different genes and participates in a variety of cellular functions through the citrullination of target proteins. The crystal structure of human PAD4 with a dimeric form was previously solved because of the enzyme’s relevance to rheumatoid arthritis. PAD6, abundant in mouse oocytes and eggs, is believed to take part in early events of embryogenesis, but its biochemical properties are little understood. Here we have purified and characterized a recombinant PAD6. A PAD6 cDNA was cloned from mouse ovary RNA and expressed in Escherichia coli through pET29 and pGEX vectors. When benzoyl-L-arginine ethyl ester was used as a substrate, no appreciable activity was detected with a cell homogenate under conditions where a human PAD4 cDNA caused significant activity. Both proteins were affinity-purified to near homogeneity. The circular dichroism spectra of PAD6 and human PAD4 were similar in the far ultraviolet region. On molecular sieving, PAD6 was eluted faster than human PAD4. The cross-linking of PAD6 with dimethyl suberimidate clearly showed six bands on an sodium dodecyl sulfate-polyacrylamide gel. These results indicate that PAD6 can constitute a hexameric structure. The purified PAD6 still showed no enzymatic activity. This unique structure and loss in enzymatic activity is strongly suggested to favor the formation of egg cytoplasmic sheets as the architectural protein.展开更多
文摘Diagnosis and management of interstitial lung diseases (ILDs), caused by lung epithelial injury followed by apoptosis, are often challenging. It has been controversial whether the SIRT1 protein, a principal modulator of longevity due to caloric restriction, ameliorates or aggravates ILD in animal models. Here we examined the effect of SRT1720, a syn- thetic activator of SIRT1, on bleomycin-induced lung injury in a mouse model and apoptosis in cultured epithelial cells. Oral intubation of SRT1720 over a period of 15 days caused body weight loss and a high mortality rate among bleomy- cin-treated mice. Histological examinations showed that the SRT1720 load increased fibrosis in the bleomycin-treated lung. An analysis of bronchoalveolar lavage fluid revealed remarkably increased numbers of inflammatory cells in the SRT1720-treated group. Moreover, the apoptosis of A549 lung cancer cells, caused by X-ray irradiation and an anti-Fas activating antibody, was promoted by SRT1720. These results indicate that SRT1720 not only aggravates bleomy- cin-induced ILD, but stimulates the apoptosis of physically and biologically stimulated A549 cells. While SIRT1 acti- vators are considered promising for the treatment of conditions such as diabetes mellitus, fatty liver, and chronic ob- structive pulmonary diseases, an excess of food containing SIRT1 activators may be harmful depending on the disease state, especially in the case of acute inflammation.
文摘The murine peptidylarginine deiminase (PAD) has five isoforms encoded by different genes and participates in a variety of cellular functions through the citrullination of target proteins. The crystal structure of human PAD4 with a dimeric form was previously solved because of the enzyme’s relevance to rheumatoid arthritis. PAD6, abundant in mouse oocytes and eggs, is believed to take part in early events of embryogenesis, but its biochemical properties are little understood. Here we have purified and characterized a recombinant PAD6. A PAD6 cDNA was cloned from mouse ovary RNA and expressed in Escherichia coli through pET29 and pGEX vectors. When benzoyl-L-arginine ethyl ester was used as a substrate, no appreciable activity was detected with a cell homogenate under conditions where a human PAD4 cDNA caused significant activity. Both proteins were affinity-purified to near homogeneity. The circular dichroism spectra of PAD6 and human PAD4 were similar in the far ultraviolet region. On molecular sieving, PAD6 was eluted faster than human PAD4. The cross-linking of PAD6 with dimethyl suberimidate clearly showed six bands on an sodium dodecyl sulfate-polyacrylamide gel. These results indicate that PAD6 can constitute a hexameric structure. The purified PAD6 still showed no enzymatic activity. This unique structure and loss in enzymatic activity is strongly suggested to favor the formation of egg cytoplasmic sheets as the architectural protein.
